1. Field of the Invention
The present invention relates to a lubricating device which discharges lubricating oil to a spindle apparatus provided in various high-speed rotary machines such as a machine tool and, especially, to the bearing of the spindle.
2. Description of the Related Art
Conventionally, in lubricating the bearing of a high-speed rotary spindle, normally, there are used lubricating devices of various types such as an oil mist type, an oil-air type, and a jet type.
The lubricating device of an oil mist type comprises an oil tank, a pump, a plunger, a pressure divider, compressed air, an electromagnetic valve, and a nozzle; and, in this device, lubricating oil is turned into a fine mist-like form, it is delivered through an air pipe using the compressed air, and it is jetted out to the interior portion of the bearing.
The lubricating device of an oil-air type comprises an oil tank, a pump, a distributor, a compressed air source, a plunger, and a nozzle; and, in this device, lubricating oil drops (0.01-0.03 cc) adjusted to a given quantity by the mechanical mechanism of the plunger is discharged into an air pipe, is delivered up to the nozzle by the compressed air, and is jetted out to the interior portion of the bearing.
The lubricating device of a jet type is a device which does not use the air source but turns lubricating oil into high pressure one using a high-pressure pump and jets out the high-pressure lubricating oil at a high speed into the interior portion of the bearing from a nozzle of which discharge diameter is narrowed.
By the way, while a current trend requests an increase in the rotation speed of the spindle device, in the lubricating devices of various types used for lubrication of the spindle device, there are found the following problems:
Firstly, in the lubricating device of an oil mist type, due to use of the compressed air, not only there arises a noise problem but also the mist-like lubricating oil scatters into the air to worsen an operation environment. Also, because of the scattering of the mist-like lubricating oil into the air, the quantity of lubricating oil to be supplied to the interior portion of the bearing is indefinite. Especially, in case where the bearing is rotated at a high speed, due to the effect of an air curtain, when dmxc2x7N is equal to or larger than 2000000 (dm expresses the pitch circle diameter of the bearing, and N expresses the rotation speed (rpm) of the bearing), the lubricating oil can be little supplied to the interior portion of the bearing, thereby raising a fear that the bearing can cause seizure.
In the lubricating device of an oil-air type, similarly to the-above-mentioned oil mist type lubricating device, since the compressed air is used, not only there arises a noise problem but also the mist-like lubricating oil scatters into the air to thereby worsen the operation environment. Also, in the high-speed rotation of the bearing, as the result of the rotation of the spindle, there is produced an air curtain. Therefore, similarly, the lubricating oil can be little supplied to the interior portion of the bearing, thereby raising a fear that the bearing can cause seizure.
Also, in the lubricating device of an oil-air type, because it is difficult to supply a fine amount of lubricating oil continuously and stably, the lubricating oil must be supplied intermittently and thus the lubricating oil is supplied at a given quantity (normally, in the range of 0.01-0.03 cc) every given interval time (normally, in the rage of 8-16 min.) into the air pipe. Therefore, since the quantity of lubricating oil to be supplied to the interior portion of the bearing varies every given time, the lubricating condition of the interior portion of the bearing varies all the time and, especially, just after the lubricating oil is supplied, a large quantity of lubricating oil enters the interior portion of the bearing, thereby causing a phenomenon that the torque of the bearing and the temperature of the bearing can vary. There is a fear that this phenomenon can have ill effects on the working precision of a machine tool.
On the other hand, in a lubricating device of a jet type, when compared with the above lubricating devices of oil mist and oil-air types, there is little found the effect of the above-mentioned air curtain but, not only because there is required an attendant device such as a high-pressure pump but also because the quantity of lubricating oil to be supplied to the bearing increases to thereby increase drag resistance, there is necessary a large motor which is used to drive the spindle, which results in the increased cost.
As a device which has solved the difficulty in the above-mentioned fine quantity adjustment of a lubricant, there are known devices which are respectively disclosed in the following patent publications.
That is, in Japanese Patent Examined Publication No. 2-15003 of Heisei, there is disclosed a device for supplying a fine fixed quantity of liquid. In this supply device, a piezo-electric element is used to allow the fine quantity adjustment of the liquid and a lubricant is delivered to a nozzle by compressed air.
In a flow control valve disclosed in Japanese Patent Examined Publication No. 7-65695, a diaphragm is disposed in one end of a magnetostrictive element and an orifice is adjusted by the expansion and contraction of the magnetostrictive element to thereby adjust the flow quantity and pressure of fluid.
In a giant magnetostrictive material pump disclosed in Japanese Patent Unexamined Publication No. 3-222877 of Heisei, the displacement of a giant magnetostrictive material is enlarged by a lever, and a diaphragm is driven by the lever to turn the pressure of the interior portion of the pump into a negative pressure or a positive pressure, thereby sucking or discharging a fluid.
In a magnetic precision pump (Magnetostrictive Pump) disclosed in U.S. Pat. Nos. 4,795,318 and 4,804,314, in the interior portion of a cylinder, there is disposed a piston which is formed of a magnetostrictive material and a voltage is applied to a coil, which is disposed in such a manner that it encloses the piston, to thereby expand and contract the piston so as to discharge a fluid in the interior portion of the cylinder.
In a giant magnetostrictive material type injection pump disclosed in Japanese Patent Unexamined Publication No. 4-81565 of Heisei, a needle valve is opened and closed by a giant magnetostrictive material to thereby inject a fixed quantity of high-pressure liquid.
However, in the above-mentioned pump using a giant magnetostrictive material or flow control valve, there are found the following problems.
The fine fixed quantity liquid supply device disclosed in Japanese Patent Examined Publication No. 2-15003 of Heisei has not solved yet a drawback caused by delivering the lubricant to the nozzle using the high-pressure air.
In the flow control valve disclosed in Japanese Patent Examined Publication No. 7-65695, the diaphragm area, to which the pressure of the liquid is applied, is larger than the sectional area of the giant magnetostrictive material and the liquid pressure is smaller than the pressure of the giant magnetostrictive material
In the giant magnetostrictive material pump disclosed in Japanese Patent Unexamined Publication No. 3-222877 of Heisei, since the displacement is enlarged by the lever, the liquid pressure is smaller than the pressure of the giant magnetostrictive material. The output of the giant magnetostrictive material increases as a magnetic field by a coil is increased. However, in case where the coil magnetic field is increased, the required volume of the coil increases accordingly. As a result of this, a device using such coil increases in size.
In the magnetic precision pump disclosed in U.S. Pat. Nos. 4,795,318 and 4,804,314, since the piston itself is made of a drive element, the pressure of the lubricant cannot be made larger than the pressure of the giant magnetostrictive material.
The giant magnetostrictive material type injection pump disclosed in Japanese Patent Unexamined Publication No. 4-81565 of Heisei does not have a function to turn the pressure of the liquid into high pressure.
The present invention aims at eliminating the drawbacks found in the above-mentioned circumstances. Accordingly, it is an object of the invention to provide a lubricating device which injects a high-precision set fine quantity of lubricant onto the lubricating surface of a rotary body at a high speed to thereby minimize an increase in torque and bearing temperature so as to be able not only to provide high torque stability and reduce the generation of noises but also to reduce the size and cost thereof, and a spindle apparatus using such lubricating device.
In attaining the above object, according to the invention, there is provided a spindle apparatus comprising a shaft, at least two bearings disposed spaced apart from the shaft in the axial direction of the shaft, each of the bearings having an inner race fitted with the shaft, and a housing fitted with the outer races of the bearings, with the inner races and outer races of the bearings being rotatable with respect to each other with rolling elements between them, the spindle apparatus further including: a lubricating device for supplying lubricating oil to the bearings at a discharge speed in the range of 10 m/sec.-100 m/sec. and in a fine discharge oil quantity in the range of 0.0005 cc/shot-0.01 cc/shot.
According to the above structure, since the discharge speed of the lubricating oil to be discharged from the nozzle is high, that is, 10 m/sec-100 m/sec., the lubricating oil can be supplied to the interior portion of the bearing positively without being influenced by an air curtain which can occur in the high-speed rotation. Also, because the discharge quantity of the lubricating oil is fine, that is, in the range of 0.0005 cc/shot-0.01 cc/shot, an increase in the temperatures of the bearings can be controlled down to a low level. Further, since there are not used attendant devices including a high-pressure pump such as a jet type, there is eliminated an increase in drag resistance which could be caused due to an increase in the quantity of the oil supplied to the bearings, so that, as a motor for driving the spindle, there can be used a motor which is inexpensive and compact.
Also, in addition to the above structure, there may be disposed a shaft rotation speed detector (tachometer) for detecting the shaft rotation speed. In this case, by controlling the supply interval and supply quantity of the lubricating oil discharged from the lubricating device based on the detect results of the shaft rotation speed detector (tachometer), a proper oil quantity of lubrication is possible with respect to the spindle rotation regardless of the spindle rotation speed, so that an ideal lubricating condition can be always obtained in the interior portion of the bearing. Also, the increase in the bearing temperature can also be controlled down to a further lower level. Further, since the lubricating oil is supplied to the interior portion of the bearing positively, a lubricating oil supply efficiency can be enhanced and the lubricating oil consumption can be reduced. Moreover, since compressed air supplied by a compressor is not used as in the lubricating device of an oil mist system or an oil-air system, the noise level is low and the oil mist can be little produced.
And, in addition to the above structure, there may be disposed a lubricating oil filter, an air bleeder sensor, and a clogging detect pressure sensor. In this case, there can be avoided troubles such as a clogged condition.
By the way, the oil supply quantity to the interior portion of the bearing, in case where dmxc2x7N is equal to or larger than 1000000, preferably; may be in the range of 0.0005 cc/min.-0.12 cc/min., and, more preferably, in the range of 0.003 cc/min.-0.12 cc/min.
Also, the inside diameter of the nozzle outlet, preferably, may be in the range of 0.08 mm-0.6 mm and, more preferably, in the range of 0.1 mm-0.5 mm.
Further, a ratio of the length L (mm) of the pipe up to the nozzle to the pipe diameter d (mm), preferably, may be 5xe2x89xa6L/d4xe2x89xa612000 mmxe2x88x923, and, more preferably, 5xe2x89xa6L/d4xe2x89xa610000 mmxe2x88x923.
Still further, according to another aspect of the invention, there is provided a lubricating device which uses magnetostrictive pump including a pump chamber for pressurizing lubricant by means of the expanding and contracting operations of a rod body formed of magnetostrictive material to be executed by applying a magnetic field to the rod body and removing the magnetic field therefrom, thereby discharging the pressurized lubricant, the lubricating device comprising: a check valve disposed in the intermediate portion of a flow passage for supplying the lubricant to the magnetostrictive pump to prevent the lubricant from flowing out from the magnetostrictive pump, and a nozzle disposed on the lubricating discharge side of the magnetostrictive pump and having a flow passage sectional area smaller than the lubricant flow passage sectional area of the check valve.
According to the present lubricating device, the rod body can be expanded due to the application of the magnetic field, and the lubricant within the magnetostrictive pump can be thereby compressed. Due to the compression of the lubricant, the pressure of the flow passage for supplying the lubricant is increased, the check valves closed, and the lubricant is discharged externally at a high speed from the nozzle. In case where the magnetic field application is cut off, the rod body is contracted to thereby increase the internal capacity of the pump, so that the lubricant is supplied into the pump through the check valve. In this operation, the air also flows in from the leading end of the nozzle. However, since the flow-in quantity ratio of the lubricant to the air is proportional to the square of the flow passage sectional area ratio of the check valve to the nozzle, the flow-in quantity of the lubricant becomes larger than that of the air, so that, in the next operation as well, the lubricant can be discharged similarly.
Further, according to the above lubricating device, the one end side of the rod body is fixed, a piston is connected to the other end side of the rod body, and the piston is slidably disposed within a cylinder to thereby form a pump chamber, while the cross sectional area of the inner surface of the cylinder is set smaller than the cross sectional area of the rod body.
In the present lubricating device, due to the expansion and contraction of the rod body, the piston within the cylinder is moved to thereby form the pump. And, the pressure of the lubricant within the cylinder is higher than the pressure generated by the rod body, which makes it possible to discharge the lubricant at a high speed.
Also, in the lubricating device, the decreased area of the pump chamber due to the expansion of the rod body is set equal to the sum of the quantity of the air flowing in from the nozzle when the rod body is contracted, a decreased volume due to compression of the lubricant that is present within the internal capacity between the check valve and the outlet of the nozzle, the increased capacity of the internal capacity due to the pressure deformation of parts forming the internal capacity, and a required discharge quantity of lubricant.
In the lubricating device, the magnetic field to be applied to the rod body is controlled while correcting it using values with variable elements taken into account, while the variable elements respectively relate to the quantity of air flowing in from the nozzle, the decreased volume due to the compression of the lubricant, and the increased capacity of the internal capacity due to the pressure deformation of parts forming the internal capacity This can avoid a discharge quantity error which could otherwise be caused by the variable elements, so that a desired discharge quantity can be obtained with high accuracy.
Further, in the lubricating device, the magnetostrictive pump includes a coil for applying a magnetic field and a control device for controlling a current to be supplied to the coil to thereby expand and contract the rod body; and, the control device, in the initial excitation stage of the coil, supplies a current until the lubricant within the pump chamber reaches such a pressure as to allow the magnetostrictive pump to obtain a desired discharge speed, after reaching this pressure, supplies a current for maintaining the pressure of the lubricant constant according to the discharge quantity of the lubricant, and further, after a desired lubricant discharge quantity is obtained, cuts off the supply current.
According to the present lubricating device, when the current is supplied to the coil from the control device, the rod body is expanded to thereby allow the piston to compress the lubricant within the pump chamber. As a result of this, the pressure within the cylinder is increased, the suction valve is closed, and the lubricant is thereby discharged externally at a high speed from the nozzle. At the then time, the control device, for example, in the initial excitation stage of the coil, supplies a current to the coil until the current reaches such a current value for the magnetostrictive pump as to be able to obtain a desired discharge speed, that is, the control device raises the current up to this current value quickly. During this, a high voltage is applied to the coil to thereby raise the current quickly against the time constant of the coil. And, after reaching the current value to be able to obtain the desired discharge speed, in order to maintain the pressure of the lubricant which decreases according to the discharge quantity of the lubricant constant, the control device supplies the current in such a manner that the capacity of the cylinder decreases by a capacity equal to the discharge quantity of the lubricant. During this, due to the time constant of the coil, the voltage is switched over to a voltage which can obtain a desired current increasing speed. Next, after the desired lubricant discharge quantity is obtained, the supply current to the coil is cut off. Thanks to this, a required lubricant pressure can be obtained in and from the early discharge stage of the lubricant and, after the start of discharge of the lubricant, the discharge speed can be maintained constant, so that the discharge of the lubricant can be carried out accurately and stably. Also, when the current is cut off, the rod body is contracted to thereby increase the internal capacity of the pump chamber, so that the lubricant can be supplied into the pump chamber through the suction valve.
Also, the above lubricating device further includes a measuring device for measuring any one of the value of a current to be supplied to the coil, a voltage value proportional to this current, and the value of a magnetic flux caused by this current; and, an abnormal condition judging device for comparing a measured value with respect to an elapsed time measured by the measuring device with a measured value in a normal condition time to thereby judge whether an abnormal condition has occurred or not, whereby, when the abnormal condition judging device judges that an abnormal condition has occurred, the lubricating device issues an abnormal signal.
According to the present lubricant device, for example, assuming that a target to be measured is a current value, in case where a current value measured at the time when a certain time has passed after the start of the supply of a current is larger than a current value (a design value) in a normal operation time, that is, in case where a time required for a current to increase up to a certain current value is shorter than a design value, it can be judged that an abnormal condition such as the clogged condition of the nozzle has occurred. On the other hand, in case where the current value measured at the time when a certain time has passed after the start of the supply of the current is smaller than the design value, that is, in case where the time required for the current to increase up to a certain current value is longer than the design value, it can be judged that an abnormal condition such as lubricant leakage has occurred. Also, assuming that the target to be measured is a voltage value or a magnetic flux value, an abnormal condition can be judged similarly. And, by issuing the abnormal signal at the time when the abnormal condition occurs, feedback control can be carried out, for example, the operation of the supply target of the lubricant can be stopped.
Further, the above-mentioned lubricating device further includes a measuring device for measuring any one of the value of a current to be supplied to the coil, a voltage value proportional to this current, and the value of a magnetic flux caused by this current; and, an air mixture judging device for comparing a measured value with respect to an elapsed time measured by the measuring device with a measured value in an air non-mixture time to thereby judge whether the air is mixed or not, whereby, in the start of the operation of the lubricant device, until the air mixture judging device judges that the air is not mixed, the lubricant device increases the current to be supplied to the coil or increases the supply frequency of the current.
According to the present lubricating device, assuming that the target to be measured is a current, in case where the air is mixed into the lubricant, the rising time of the current to be measured is long, which makes it possible to judge the presence or absence of the mixed air. Also, assuming that the target to be measured is a voltage value or a magnetic flux value, an abnormal condition can be judged similarly. And, in the start of the operation of the lubricating device, until it is judged that the mixed air is not present, by increasing the current to be supplied to the coil or by increasing the supply frequency of the current, or by increasing both the current and the supply frequency of the current, the discharge quantity and discharge cycle of the magnetostrictive pump can be increased, so that the lubricant can be quickly sucked into the pump from the tank and the air bleed can be completed in a short time.
To sum up the above facts, by using the super fine quantity oil lubricating system, a lubricating oil forced circulating device, a heat exchanger, a lubricating oil collecting device, and other attendant devices such as compressed air, which are used in the conventional lubricating systems such as a lubricating system of an oil mist, a lubricating system of an oil-air type and a lubricating system of a jet type, can be simplified; the noise level can be controlled down to a low level, which can be consideration for environment. And, the consumption of the lubricating oil can be reduced, the bearing torque can be enhanced in stability, and the bearing temperature increase can be controlled down to a low level, thereby being able to enhance the rotation accuracy of the spindle Therefore, according to the present invention, there can be provided a spindle apparatus which is more advantageous than the conventional spindle apparatus using the related lubricating methods.